Veteran Liberal MP Bronwyn Bishop has pledged to be "impartial" in her new role as Speaker of the 44th Parliament.

More than two months after the federal election, MPs and senators have been sworn in and the new Parliament officially opened.

Prime Minister Tony Abbott, who nominated Mrs Bishop to the Speaker's chair, prompted the first jeer from Opposition benches by saying that "this chamber should always be a place of spirited debate, but it should never be a place where motives are impugned or characters assassinated".

The Opposition put up its own nominee for Speaker, Member for McEwen Rob Mitchell, but lost the first vote of the new Parliament along party lines.

Labor has protested against Mrs Bishop's intention to still attend party room meetings while in the Speaker's role.

Manager of Opposition Business Tony Burke said the elevation was "reminiscent of the Harry Potter novel" in which the villainous Dolores Umbridge is made headmistress of Hogwarts School of Witchcraft and Wizardry.

"When they all return to Hogwarts, Dumbledore is gone and Dolores Umbridge is now in charge of the school," he said.

But the new Speaker, who has been in Parliament for 26 years, insists the Opposition need not worry.

"I mean to be impartial," she told Parliament.

"The comments that I have made about attending party meetings is simply that I am a Liberal - but we don't deal with tactics and I wouldn't be part of that.

"But in this chair, I will act impartially. That is the responsibility that goes back to 1377."

"So when Joe Hockey moves the increase in the debt cap in the House of Representatives, we will move an amendment to only authorise an increase to $400 billion."

But Mr Abbott says the Government needs a new debt limit of $500 billion to put "Labor's debt legacy" in the past.

"The Treasury advice is that based on the mess we have inherited from Labor, that gross debt will peak significantly in excess of $400 billion," he said.

"If the Labor Party and Opposition members want to put their shameful fiscal history behind them, the best thing they can do is allow this legislation to pass, deal with Labor's debt legacy, and let the repair squad get in and fix Labor's mess."

The Greens have indicated they will also vote against the increase in the Senate, a move which would kill it off until the Upper House changeover next July.

"We are not inclined to support the Government's increase, we can see some sense in what Labor is proposing," Greens MP Adam Bandt said.

"It's up to the Government to justify why it wants to go as high as it wants to go.

"In default of a satisfactory explanation from the Government, then Labor's position seems to make a lot of sense."

When he announced the changes, Mr Hockey would only say that recent trends indicated that net debt would "exceed $400 billion".

"Before the election, the Liberal Party said we've got to cut our debt and bring our debt down. The first thing that happens after the election is Joe Hockey increases the debt ceiling by another $100 billion," he said.

"While we have to raise our debt ceiling because of the precarious position of the economy, and we've got to think about the people that need to be supported in our society that are less fortunate than ourselves, we shouldn't be in that position.

"The Government has policy options available to it which wouldn't require us to do that."

But the day has been dominated by pomp and ceremony, beginning with a Welcome to Country ceremony which was shifted to Parliament's Great Hall because of wet weather.

Ngambri elder Matilda House gave the Prime Minister a "fighting boomerang", telling Mr Abbott "it's good for hunting".

Tomorrow, MPs will return to Parliament for the expected tabling of legislation to repeal the carbon pricing scheme and the first Question Time.